1. Field of the Invention
The present invention relates to a zoom lens, in particular to a small, wide-angle zoom lens having high zoom ratio for use in a video camera or digital camera.
2. Description of the Related Art
There is a demand for video cameras and digital cameras having a wide angle of view and high zoom ratio in recent years with an increase in the variety of application in shooting with such cameras. In addition, the size and thickness of zoom lenses for use in such cameras have been made smaller.
To achieve reduction in the size of zoom lenses with respect to the direction along the optical axis, various optical systems having a prism that bends the optical path provided in the lens unit closest to the object side of the optical system have been developed.
Slimming and size reduction of taking optical systems lead to weight reduction of cameras, which can sometimes lead to deterioration in image quality caused by camera shake in hand-held shooting. Many zoom lenses in which one or more lenses in the optical system are shifted in directions perpendicular to the optical axis to cancel blur of picked-up images have been developed.
Japanese Patent Application Laid-Open Nos. 2008-261996, 2009-192771, 2010-097127, 2011-070220, and 2011-070222 disclose prior art optical systems having a prism provided in the lens unit closest to the object side to bend the optical path, in which one or more of lenses in the optical system are shifted in directions perpendicular to the optical axis to stabilize image.
Japanese Patent Application Laid-Open Nos. 2009-236973, 2011-095504, 2008-129238, 2010-170084, and 2011-095505 disclose optical systems having a prism provided in the lens unit closest to the object side to bend the optical path. The optical systems disclosed in these patent documents are zoom lenses including five lens units having, in order from the object side, positive, negative, positive, negative, and positive refractive powers respectively. This configuration contributes to reduction in the size of the optical system.